This project will focus on the objective assessment of hearing status using measurements of the auditory brainstem response (ABR). The goal is to provide the more reliable and complete information about auditory function based on analyses of ABR data. Both stimulus delivery and response evaluation aspects of ABR measurements will be addressed. This project proposes to (1) determine whether power or pressure is the more appropriate reference for specifying stimulus level, (2) establish test parameters for a recently developed ABR detection statistic called Scor, (3) develop an efficient threshold-search strategy that will allow automated estimation of ABR thresholds, (4) investigate possible improvements in both wideband and low-frequency stimuli, and (5) evaluate the effectiveness of automated ABR threshold estimation at predicting the occurrence and magnitude of hearing loss. These objectives will be accomplished through efforts directed toward (1) ABR measurement system software development, (2) refinement of signal processing algorithms, (3) ABR measurements from both normal hearing and hearing-impaired subjects, and (4) data analyses using principles of statistical decision theory. The results of these experiments will have both theoretical and practical significance and should increase the power of the ABR measurement as a tool for the assessment of auditory function. The work proposed in this project will lead to a more fundamental understanding of mathematical models of response detection. We have chosen to initiate these efforts with ABR measures which are the most reliable auditory evoked potentials in humans; however, this work has applications for other, less reliable evoked potentials that presumably assess higher levels of the human auditory system.